The spectral reflectance of a plant compared to that of soil can be used to detect the presence of a plant on the ground. This is shown in FIG. 1, which is an exemplary plot illustrating the reflectance versus wavelength of a living plant 1 compared to that of bare soil 2. Due to the differences between the spectral reflectance characteristics, it is possible to differentiate the living plant 1 from the bare soil 2. For example, light beams of two different wavelengths W1, W2 can be transmitted toward the ground, and the intensities of the different wavelengths of scattered light returning from the ground can be compared to determine if there is a plant 1 or just bare soil 2.
Detecting a plant in this manner can be useful to reduce the amount of herbicide required to eradicate weeds in a field. For example, a field may be scanned using light beams of two different wavelengths, and each time the spectral reflectance characteristic of a weed is detected, a valve may be opened to spray herbicide on the weed. A considerable savings in herbicide may be realized since it is not sprayed unnecessarily onto the bare soil.
Improved methods for detecting the presence of plants on the ground are desired.